METHOD FOR TESTING A TRANSCEIVER, AND A BASE STATION OF A TIME-DIVISIONAL RADIOCOMMUNICATION SYSTEM

Abstract: The invention relates to a method for testing a transceiver unit (1) of a time-divisional radiocommunication system. In order for a simple and reliable test method to be achieved, the method comprises assigning at least two free time slots for use, selected in such a manner that when the transmitter (2) of the unit (1) transmits on the first selected time slot, the receiver (3) of the unit (1) simultaneously receives the second selected time slot. A predetermined test signal is transmitted by the transmitter (2) using the first selected time slot. The transmitted signal is converted into the reception frequency of the unit and supplied to the receiver (3), which receives the second selected time slot. The signal obtained from the output of the receiver is compared with the test signal supplied to the transmitter. The invention also relates to a base station of a time-divisional radiocommunication system, to which the method according to the invention can be applied.

Description: Method for testing a transceiver, and a base station of a time-divisional radiocommunication system The invention relates to a method for testing a transceiver unit in a time-divisional radiocommunica¬ tion system, said method comprising supplying a prede¬ termined test signal from the transmitter to the receiver, and subsequently comparing the test signal transmitted with the test signal received, and to a base station of a time-divisional radiocommunication system, said base station comprising at least one transceiver unit and a test unit for testing the operation of the transceiver unit, said test unit comprising mixing means for converting the test signal transmitted by the trans- mitter of the transceiver unit from transmission frequency into reception frequency, the output of said mixing means being arranged to supply the test signal of the reception frequency to the receiver, and control means for supplying test data to the transmitter of the transceiver unit and for comparing the output signal of the receiver with the test data supplied to the trans¬ mitter. In this application the term transceiver unit refers to a unit which comprises a transmitter and a receiver and which can be mounted in a base station of a time-divisional radiocommunication system (TDMA = Time Division Multiple Access), such as the GSM system, where it is connected to the antenna connections of the base station. To ensure the operation of a transceiver unit, it is previously known to use a separate test device connected between the antenna connections of the trans¬ mitter and the receiver. If the transceiver unit is part of such a base station of a radiocommunication system that comprises several transceiver units, the separate test device is positioned after the transmitter combiner of the base station. In this case, the same test unit is used for testing several transceiver units. The test device converts the test signal transmitted by the transmitter of the unit into the reception frequency of the receiver of the unit and supplies it to the input of the receiver after a short delay, which in the trans¬ ceiver concerned must occur between the transmission and reception of one channel. According to the GSM Speci- fications, for example, this delay is three channel time slots. The operation of the transceiver is checked by comparing the signal obtained from the output of the receiver with the test data supplied to the transmitter. The structure of known test devices is very complicated owing to the delay components they contain for providing the delay mentioned above, e.g. the delay of three time slots according to the GSM Specifications. In the known test units, these delay components are either analog or digital, in which case they comprise an analog-to-digital converter, a digital shift register and a digital-to-analog converter. The object of the present invention is to obviate the problem described above and to provide a simple and reliable method for testing the operation of a transceiver unit, and to provide a base station to which the method can be applied. These objects are achieved with a method according to the invention, which is characterized by assigning at least two free time slots for use, selected in such a manner that when the transmitter of the transceiver unit transmits on the first selected time slot, the receiver of the trans¬ ceiver unit simultaneously receives the second selected time slot, supplying a predetermined test signal to the input of the transmitter, transmitting the predetermined test signal by the transmitter using the first selected time slot, converting the output signal transmitted on the first selected time slot into the reception frequency of the transceiver unit, supplying the signal of the reception frequency to the receiver, which receives the second selected time slot, and comparing the signal obtained from the output of the receiver with the test signal supplied to the transmitter. The invention also relates to a base station which is characterized in that said base station comprises means for selecting two free time slots of the transceiver unit and for assigning them for the test, the control means of the transceiver unit conducting the testing of the operation of the unit using the selected time slots in such a manner that the transmitter transmits a test signal using the first selected time slot and the receiver receives the test signal using the second selected time slot. The invention is based on the idea that the testing of a transceiver unit is much simpler than with the known solutions if the test is conducted by utilizing two time slots of the transceiver unit. In this case it is not necessary to provide additional delays between the transmission and reception of a test signal. The fact that no additional delays are needed simplifies the structure of the test unit considerably as compared with the known solutions. The most signific¬ ant advantage of the base station according to the invention is thus the simplicity of the structure of its test unit, which is due to the fact that the additional delay components used in the known test units are not needed at all. In a preferred embodiment of the base station according to the invention, the test unit is integrated into the transceiver unit. In this way it is possible to avoid the problem pertaining to the use of an external test unit, i.e. that the one conducting the test must have a considerable amount of information, for example, on the transmission frequencies used by the radiocommunication system/base station concerned so that the other traffic in the radiocommunication system/base station is not disturbed during the test. If a separate external test unit is used, the transceiver unit to be tested and the test device to be used must be separately adjusted before each test to avoid the above-mentioned disturbances. The preferred embodiments of the base station and method according to the invention are disclosed in the accompanying dependent claims 2 and 4 to 7. In the following, the invention will be described by means of a preferred embodiment and with reference to the appended drawings, in which Figure 1 shows part of a preferred embodiment of the base station according to the invention, and Figure 2 is a schematic representation of how the time slots to be used should be selected for the testing of a transceiver unit of the GSM system. Figure 1 shows part of a preferred embodiment of the base station according to the invention. Figure 1 illustrates a transceiver unit 1 of a base station in the GSM system. The unit 1 illustrated in the figure tests the operation of the components of its transmitter 2 and receiver 3 by means of a loop integrated into the unit. The loop shown in the figure consists of components 7, 9 and 10 and is preferably integrated into each transceiver unit of the base station. When the unit 1 is tested, the base station controller 4 selects two free time slots, e.g. time slots 4 and 1 (shown in Figure 2), which do not carry any traffic at that par¬ ticular moment. The time slots are selected in such a manner that when the transmitter 2 of the transceiver unit 1 transmits on the first selected time slot, e.g. on time slot 4, the receiver 3 receives the second selected time slot, e.g. time slot 1. When the time slots to be used have been selected, the control unit 5 in the baseband section 13 of the transceiver unit 1 switches on the oscillator 6 of the transceiver unit. The oscillator 6 is thus switched on before the actual test is started to allow it to settle before the actual test. A suitable settling time is, for example, 10 ms. When the actual test is conducted, the control unit 5 of the transceiver unit 1 switches on a mixer 7 by means of an RF switch 8 while supplying predetermined test data to the input of the transmitter 2 through a frame unit 11. The transmitter 2 transmits the test data supplied to it, using the first selected time slot, e.g. time slot 4. The output of the transmitter 2 is connected via a directional coupler 9 to the mixer 7, which under the control of the control unit 5 operates during the test period, converting the test signal into reception frequency. The output of the mixer 6 is connected to a directional coupler 10, by means of which the signal of reception frequency is supplied to the input of the receiver 3 on the second selected time slot, e.g. time slot 1. Thus, unlike the known test devices, the test loop consisting of components 7, 9 and 10 does not comprise any components intended to introduce delay. The output signal of the receiver 3 is supplied through the frame unit 12 to the control means 5, which compares the received test signal and the predetermined test data supplied to the transmitter 3 through the frame unit 11. The comparison can be made, for instance, by calculating the bit error ratio (BER) and comparing it with a predetermined reference value. If the bit error ratio obtained by calculation exceeds the refer¬ ence value, the control means 5 sends information on this to the base station controller 4. If the transceiver unit to be tested is of a type comprising a diversity branch (DIV RX), this branch can also be tested in addition to the actual receiver branch. If it is then observed that the normal receiver gives high BER results and the diversity branch gives normal BER results, the transceiver unit can be adjusted so as to use only the diversity branch, whereby the diversity function is naturally lost. Figure 2 is a schematic representation of how the time slots to be used should be selected for the testing of a transceiver unit in the GSM system. The GSM Specifications require that a mobile station should have a delay of three time slots between reception and trans¬ mission. Figure 2 illustrates the effect of a delay of three time slots on the operation of a base station. When the transmitter (indicated by reference number 2 in Figure 1) of a given transceiver unit in a GSM base station transmits on time slot 4, the receiver (indicated by reference number 3 in Figure 1) of the same transceiver unit simultaneously receives time slot 1. The structure and operation of the GSM system is described in The GSM System for Mobile Communications by M. Mouly and M-B. Pautet, Palaiseau, France, 1992, ISBN: 2-9507190-0-7. According to the invention, two time slots must thus be assigned for the test in order that the need of delay components in the test loop (components 7, 9 and 10 in Figure 1) could be avoided and the test signal transmitted by the transmitter could be immediately supplied to the input of the receiver. The above description and the accompanying drawings are intended merely to illustrate the invention without limiting it. Thus the embodiments of the method and base station according to the invention can vary within the scope of the appended claims.

Claims: Claims 1. A method for testing a transceiver unit in a time-divisional radiocommunication system, said method comprising supplying a predetermined test signal from the transmitter (2) to the receiver (3), and subsequently comparing the test signal transmitted with the test signal received, c h a r a c t e r i z e d by assigning at least two free time slots for use, selected in such a manner that when the transmitter (2) of the transceiver unit (1) transmits on the first selected time slot, the receiver (3) of the transceiver unit (1) simultaneously receives the second selected time slot, supplying a predetermined test signal to the input of the transmitter (2), transmitting the predetermined test signal by the transmitter (2) using the first selected time slot, converting the output signal transmitted on the first selected time slot into the reception frequency of the transceiver unit, supplying the signal of the reception frequency to the receiver (3), which receives the second selected time slot, and comparing the signal obtained from the output of the receiver with the test signal supplied to the transmitter. 2. A method according to claim 1, c h a r a c ¬ t e r i z e d in that the unit to be tested is a trans- ceiver unit (1) of a base station in a GSM system. 3. A base station of a time-divisional radio- communication system, said base station comprising at least one transceiver unit (1) and a test unit for testing the operation of the transceiver unit (1), said test unit comprising mixing means (7) for converting the test signal transmitted by the transmitter (2) of the transceiver unit from transmission frequency into reception fre¬ quency, the output of said mixing means being arranged to supply the test signal of the reception frequency to the receiver (3), and control means (5) for supplying test data to the transmitter (2) of the transceiver unit (1) and for comparing the output signal of the receiver (3) with the test data supplied to the transmitter, c h a r a c ¬ t e r i z e d in that said base station comprises means (4) for selecting two free time slots of the transceiver unit and for assigning them for the test, the control means (5) of the transceiver unit (1) conducting the testing of the operation of the unit (1) using the selected time slots in such a manner that the transmitter (2) transmits a test signal using the first selected time slot and the receiver (3) receives the test signal using the second selected time slot. 4. A base station according to claim 3, c h a r a c t e r i z e d in that it is a base station of the GSM system. 5. A base station according to claim 3 or 4, c h a r a c t e r i z e d in that the test unit is integrated into the transceiver unit (1). 6. A base station according to any one of preceding claims 3 to 5, c h a r a c t e r i z e d in that the means (4) for selecting the time slots to be used is the base station controller. 7. A base station according to any one of preceding claims 3 to 6, c h a r a c t e r i z e d in that the control unit (5) of the transceiver unit (1) in the base station comprises means for calculating the bit error ratio on the basis of comparison between the output signal of the receiver (3) and the test data supplied to the transmitter (1).

Inventors: JYLHAE RAIMO, JYLHAE, RAIMO
Applicants: JYLHAE RAIMO, NOKIA TELECOMMUNICATIONS OY, JYLHAE, RAIMO
Application year: 1994
Main classification: H04B17
IPC codes: H04B17, H04W24